1. Field of the Invention
The invention relates to an apparatus for recording and reproducing information with a ring buffer for recording and reproducing video signals by using its area circularly.
2. Description of Related Art
In recent years, hard disk recorders are attracting a great attention as a recording device in which a program provided by television broadcast or the like is recorded onto a hard disk instead of a video tape. When a hard disk is used as a recording medium, for example, while the program which is broadcast is being recorded, the recorded program can be simultaneously reproduced (hereinafter, referred to as a time shift reproduction). A ring buffer area is provided in the hard disk in order to realize the time shift reproduction.
FIG. 1 is a diagram for explaining the recording and reproducing operations in the ring buffer area when performing the time shift reproduction.
In FIG. 1, a write position WP indicates a present recording position in the ring buffer area and a read position RP indicates a present reproducing position in the ring buffer area. Those positions WP and RP move gradually from a head position to a last position of the ring buffer area independently, as shown by blank arrows in FIG. 1 respectively. When each of the positions WP and RP reaches the last position, the position returns to the head position and again gradually moves toward the last position. That is, in the ring buffer area, the continuous recording and reproducing operations in a range from the head to the last of the area are independently executed, and the operations are repeated circularly in the ring-buffer area. The speed at which each of the positions WP and RP moves depends on a bit rate of a video signal of a broadcast program selected as a target of recording or reproduction.
By the operations described above, at the time of the time shift reproduction, the recorded broadcast program is reproduced from the position RP while the broadcast program provided by the television broadcast is being recorded to the position WP in the ring buffer area.
In the digital broadcast channel, broadcast programs of different bit rates such as HDTV (High Definition Television) broadcast programs of high picture quality and SDTV (Standard Definition Television) broadcast programs of standard picture quality exist mixedly. Therefore, while an HDTV broadcast program of the high bit rate is being recorded, if an SDTV broadcast program of the low bit rate is reproduced in a state where the write position WP and the read position RP are close to each other as shown in FIG. 1, a state such that the WP outruns the RP occurs. If the write position WP outruns the read position RP, a portion (the SDTV broadcast program) to be reproduced will be overwritten progressively by the contents of the HDTV broadcast program.